for a start, you should tweak your BT client settings to try to max your connection speed. here's a useful guide:
9 BitTorrent how-to’s | TorrentFreak

also, u may not be maxing out your connection speed because you're DLing public torrents off Mininova/Torrentspy, which usually don't have good seed/leech ratio. try getting on private trackers like demonoid, which tend to have better seeded torrents.